In a typical spark ignited internal combustion engine, a spark plug is threadably inserted into a threaded opening in the engine head to provide the spark in the engine combustion chamber. The spark plug has a threaded base for mounting, as described, and an elongated body portion, the body portion usually including an outer shell of an electrical insulating material, such as porcelain, the spaced electrodes extending from the bottom of the spark plug base project into the engine's combustion chamber. The spark plug is designed to develop a spark across the spaced electrodes to ignite the fuel/air mixture in the engine combustion chamber.
The elongated body of the spark plug extends outwardly from the engine head and terminates in an outboard terminal post. The outboard terminal post is electrically connected to the center electrode within the combustion chamber. A lead wire is connected to the outboard terminal post for the selective application of electrical current to effectuate a spark across the spaced electrodes disposed within the combustion chamber. The wire is typically housed in a boot or cover formed of a relatively soft flexible material such as rubber of plastic. The wire is connected to the outboard terminal post by a socket formed by a resiliently biased metal clip which compressively engages the post. The boot also extends over the body portion of the spark plug to partially cover the porcelain insulating material. The boot thus not only houses and protects the wire, it also protects the body of the spark plug from moisture, grease and other contaminants.
The need to protect the wire from physical damage has increased in recent years for several reasons. First, many modern spark plug wires are formed of carbon impregnated strands which are more susceptible to damage then conventional copper wiring. Further, in the case of modern automobile engines, it is common practice to house the engines in smaller and smaller areas and to place the spark plugs, and boots covering them, in relatively inaccessible areas within the engine compartment. Specifically, the spark plugs and boots are frequently disposed in relatively deep recesses of the engine head which are partially obstructed by a multitude of valve covers, hoses, cables, and other engine components and accessories. Consequently, mechanics working on the engines are often relegated to awkwardly grasping and squeezing the boot and the wires in an attempt to remove them. This stretches and distorts the wire and boot leading to a possible interruption in the efficient transmission of the electrical pulses to fire the spark plug. This in turn results in erratic engine performance. In extreme cases, the mechanic may attempt to use a pair of pliers for forcibly removing the boot from the spark plug. It is not uncommon to break or crack the porcelain portion of the plug in this instance, necessitating replacement even if not otherwise needed.
In order to ameliorate the problems noted above, several tools have been developed in recent years to remove boots from spark plugs. In U.S. Pat. No. 4,125,938, for example, a spark plug boot removing tool is disclosed with a pair of pivoted scissor-like levers used to engage the underside of a spark plug boot by squeezing the levers together in a scissor-like action. Once the scissor-like levers are squeezed together, oppositely disposed lips at the ends of the levers are brought into engagement with the underside of the boot, and the tool is pulled outwardly from the engine to thereby pull the boot off the spark plug.
Another tool for removal of spark plug boots is disclosed in U.S. Pat. No. 4,202,088. This latter mentioned tool is basicially an L-shaped hook with an insulated handle. The smaller of the L-shaped hook's legs has a semi-circular recess adapted for engagement with the underside of the spark plug boot. When the recess engages the underside of the boot, the tool is pulled away from the engine to force removal of the boot from the spark plug.